Mental disorders will be studied and analyzed with a view to determining the genetic components in their etiology, and where possible the mode of genetic action determined. Affective disorders, as well as other disorders, will be studied in families and large pedigrees, and any genes found to be involved mapped on the human genome by linkage analysis. New statistical techniques will be devised for this purpose, allowing for both qualitative and quantitative multifactorial traits, single- and multiple-generation data. Appropriate computer programs will be written, and applied both to data that have already been collected and to data that will be collected with the special purpose of identifying major genes by segregation analysis and by searching for linkage relationships between such genes and polymorphic marker genes in blood. The statistical methods will be tested for power and robustness by simulation methods. This research will lead to a more complete understanding of the determinants involved in the mental diseases studied, to more accurate genetic counselling, and hence to increased possibilities for prevention and/or early treatment. BIBLIOGRAPHIC REFERENCES: V. L. Tanna, G. Winokur, R. C. Elston and R. C. P. Go. "A linkage study of depression spectrum disease: the use of the sib-pair method", Neuropsychobiology 2, 1976, 52-62. G. Winokur, V. L. Tanna, R. C. Elston and R. C. P. Go. "Lack of association of genetic traits with alcoholism: C3, Ss, ABO systems", Journal of Studies on Alcohol 37(9), 1976, 1313-1315.